1. Field of the Invention
The present invention relates to a semiconductor light emitting element device. In particular, the present invention relates to a semiconductor light emitting device having an electrode made of a conductive oxide.
2. Discussion of the Related Art
Semiconductor light emitting devices have been conventionally known in which a p-type semiconductor layer and an n-type semiconductor layer are stacked onto a substrate and electrodes are electrically connected to the respective p-type and n-type semiconductor layers. Also, an electrode that is electrically connected to the p-type semiconductor layer has been known in which an electrode made of a transparent material is formed on the entire surface of the p-type semiconductor layer and a metal electrode is formed thereon.
In the semiconductor light emitting device having such a configuration, a transparent thin metal film or a conductive oxide film of ITO (Indium Tin Oxide), ZnO, In2O3, SnO2, or the like, is used as the electrode formed on the entire surface of the p-type semiconductor layer (see Reference 1: Japanese Laid-Open Publication Kokai No. 2000-164922 and Reference 2: Japanese Laid-Open Publication Kokai No. 2001-210867, for example).
However, poor transmittance of the thin metal film limits the improvement of the light extraction efficiency.
A conductive oxide film such as ITO has a transparency so that the light extraction efficiency is generally excellent. However, there has been a problem that sufficient light extraction efficiency cannot be obtained according to the thickness and the composition of the film.
Generally, a pad-electrode made of metal is disposed on the electrode made of a conductive oxide in order to connect to an external member such as a wire.
However, the pad electrode is relatively thick and impenetrable to light. Therefore, in addition to the problem that emitted light can not be extracted from the region having the pad electrode, light is absorbed by the pad electrode and the loss in extracting light increases.